Fluid motor drive for lifting device such as a winch with accumulated pressure starting after brake release

ABSTRACT

A fluid pressure drive system for rotating a lifting device such as a winch includes a fluid motor having a drive shaft adapted to be connected to the winch which is engaged by a brake which may be actuated to stop the shaft by biasing means such as a spring. The fluid motor is driven by a pump which has a fluid pressure discharge connected to the motor which is also connected through a line to an accumulator. During pump operation the accumulator is charged with the pump operating pressure through a one way valve so that the accumulator stores the operating pressure during the operation of the motor to move the winch. The brake is released by forcing a fluid piston against the force of its biasing means to a releasing direction under the influence of actuating pressure which is supplied from a separate actuating pressure source. The actuating pressure source is connected through a control valve to a throttle and to a fluid pressure cylinder in which the fluid pressure piston which actuates the brake is movable. When the brake is applied the control valve is set so that the cylinder is vented to the atmosphere so that the biasing means may press the piston into an operative or brake engagement position. When the pump driving the fluid motor which operates the winch is stopped the control member is actuated to provide an actuating pressure connection through the throttle and to the control cylinder but also to a release valve for the accumulator pressure which is first connected to the line connected between the pump discharge and the motor to insure that the motor is held under operating pressure. The throttle in the line between the valve control and the brake control cylinder is set to regulate the pressure to the brake control cylinder in order that the brake may be released only after the accumulator pressure is communicated to the drive motor in order to insure that the drive motor is not subjected to the immediate loading of the winch would would cause a rapid unwinding of the winch.

United States Patent 1. 1

Behrend 1 Mar. 18, 1975 FLUID MOTOR DRIVE FOR LIFTING DEVICE SUCH AS A WINCH WITH ACCUMULATED PRESSURE STARTING AFTER BRAKE RELEASE Volkmar Behrend, Bad Schwartau, Germany [73] Assignee: Qrenstein 81 Koppel AG, Lubick,

Germany [22] Filed: July 23, 1973 [21] Appl. No.: 382,019

[75] Inventor:

[30] Foreign Application Priority Data Aug. 19, 1972 Germany 2240940 [52] U.S. Cl 303/10, 60/413, 60/905, 192/3 N, 254/150 FH [51] Int. Cl B60t 13/16,B66d 1/30 [58] Field of Search 303/10, 68, 80; 192/3 N;

Primary ExaminerDuane A. Reger Assistant Examiner-Gregory W. OConnor Attorney, Agent, or Firm-McGlew & Tuttle 57 ABSTRACT A fluid pressure drive system for rotating a lifting device such as a winch includes a fluid motor having a drive shaft adapted to be connected to the winch which is engaged by a brake which may be actuated to stop the shaft by biasing means such as a spring. The fluid motor is driven by a pump which has a fluid pressure discharge connected to the motor which is also connected through a line to an accumulator. During pump operation the accumulator is charged with the pump operating pressure through a one way valve so that the accumulator stores the operating pressure during the operation of the motor to move the winch. The brake is released by forcing a fluid piston against the force of its biasing means to a releasing direction under the influence of actuating pressure which is supplied from a separate actuating pressure source. The actuating pressure source is connected through a control valve to a throttle and to a fluid pressure cylinder in which the fluid pressure piston which actuates the brake is movable. When the brake is applied the control valve is set so that the cylinder is vented to the atmosphere so that the biasing means may press the piston into an operative or brake engagement position. When the pump driving the fluid motor which operates the winch is stopped the control member is actuated to provide an actuating pressure connection through the throttle and to the control cylinder but also to a release valve for the accumulator pressure which is first connected to the line connected between the pump discharge and the motor to insure that the motor is held under operating pressure. The throttle in the line between the valve control and the brake control cylinder is set to regulate the pressure to the brake control cylinder in order that the brake may be released only after the accumulator pressure is communicated to the drive motor in order to insure that the drive motor is not subjected to the immediate loading of the winch would would cause a rapid unwinding of the winch.

5 Claims, 1 Drawing Figure FLUID MOTOR DRIVE FOR LIFTING DEVICE SUCH AS A WINCH WITH ACCUMULATED PRESSURE STARTING AFTER BRAKE RELEASE BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION This invention relates in general to the drive for lifting devices such as winches and in particular to a new and useful fluid motor drive which includes means for applying a fluid pressure to the drive motor when a brake acting on the drive shaft is released.

2. DESCRIPTION OF THE PRIOR ART Many types of hydrostatic drives having either opened or closed circuit connections for machines such as winches and particularly lifting winches are known and such machines include a stopping or holding brake. With such drives it is a known procedure to shut off the flow of hydraulic fluid and after the fluid has come to a standstill to engage the brake. The shutting off of the fluid can be carried out in various ways. One possibility comprises bringing the driving motor of the hydraulic pump to a standstill. Another possibility is the use of an adjustable pump which is set to deliver a zero output so that the hydraulic fluid then ceases to flow. In all cases the brake only comes into action when the flow of the hydraulic fluid ceases in order to avoid damage to the holding brake. With such a hydrostatic drive system there is the disadvantage that after the stopping of the drive and the engagement of the holding brake, the fluid pressure in the pressure circuit is not maintained at a value sufficient to hold the load but drops to a feed pressure because of leakage losses or fluid in the motor and in the hydraulic pump within a few seconds. This has the result that when the brake is released during restarting of the hydraulic motor and the pump operating pressure comparable to the full load pressure is not reached for a short time, the load causes a sudden turning of the hydraulic motor in a reverse direction. This means that the load will suddenly fall for at least a short distance. In addition there is a danger that the hydraulic motor will become damaged. When the load suddenly sinks there is also a unallowable overload on the gearing which is locatedbetween the hydraulic motor and the winch drum so that the gear teeth are subject to undue wear. In addition a negative pressure is produced at the low pressure side of the hydraulic motor and this results in a cavitation action.

SUMMARY OF THE INVENTION In accordance with the invention there is provided a fluid motor actuated drive for a winch in which the shaft of the fluid motor is engaged by a brake which is actuated only after an accumulator which stores pres sure at operating pressure of the pump is connected into the pressure line between the pump and the.drive motor. Thus when the brake is released the sudden compression of the fluid in the pressure conduit by the hydraulic motor is avoided. In addition the construction avoids possible damage to the gearing between the hydraulic motor and the operating machine such as a winch or rope drum.

In a preferred arrangement of the invention a throttle is interposed in an actuating pressure line leading to a brake control cylinder having a movable brake operating piston therein. The throttle regulates the flow of actuating pressure to the piston for the release of the brake and insures a flow to a control valve for an accumulator to insure that the accumulator discharges into the pressure line connected between the pump and the drive motor to maintain the drive motor under operating pressure. The throttle member insures a delay of the actuation of the brake until the accumulator pressure is connected behind the drive motor. The throttle can be adjustable in order to regulate the delay in accordance with operating conditions.

Accordingly it is an object of the invention to provide an improved fluid motor driven lifting device such as a winch which includes a fluid motor having a drive shaft which is engaged by a braking member which is released by an actuating pressure which is also employed to control the release of an accumulator pressure behind the drive motor before the brake is fully released.

A further object of the invention is to provide a fluid motor driven lifting device such as a winch which is simple in design, rugged in construction and economical to manufacture.

For an understanding of the principles of the invention reference is made to the following description of a typical embodiment thereof as illustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The only FIGURE of the drawing is a schematic representation of a hydraulic control system for a fluid motor driven winch constructed inaccordance with the invention.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings in particular the invention embodied therein comprises a drive for a lifting winch which includes a hydraulic pump 1 having a discharge line or high pressure conduit 2 which is connected to a hydraulic motor 3 and a return conduit 4 which connects back to the pump 1. The fluid motor 3 has a drive shaft 5 which is connected through gearing inside of a winch drum 6 to operate, that is rotate the drum 6. A brake mechanism generally designated. 7 includes a brake disk 20 carried on the shaft 5 which is braked by a surrounding brake shoe 20 which is actuated by a braking piston 22 which is movable in a brake control cylinder 24. Biasing meansin the form of a spring 26 acts on the piston 22 to hold it in a braking position in which the shaft 5 will be stopped.

In accordance with the invention means are provided to supply an operating fluid pressure to the pressure line 2 before the brake is released and before the piston 22 is moved against the biasing spring 26 to effect such release. These means include an accumulator 10 which is connected through an accumulator pressure line 8 to the fluid pressure line 2. The accumulator pressure line 8 includes a combination pressure release valve and check valve 9 which includes a check valve portion 9a which permits the accumulation of an operating pressure in the accumulator 10 by flow from the pressure line 2 through the accumulator pressure line 8 to the accumulator 10 during operation of the pump 1.

' An actuating pressure source 28 is connected to a control valve for the actuating pressure 14 which in turn is connected through an actuating pressure line 11 to the control cylinder 24. The actuating pressure line 11 contains a throttle valve control 12 which provides an adjustable pressure control delay in communicating an actuating pressure to the fluid control cylinder 24. A by-pass line 12a is provided in the line 11 which permits a pressure relief from the control cylinder 24 through the control valve 14 and to a sump 30 when the brake is actuated and the shaft 5 is stopped. When the pump 1 is to be started again to drive the fluid motor 3 pressure from the accumulator is admitted from the accumulator pressure line 8 to the pressure line 2 which communicates with the fluid motor 3 under the control influence of actuating pressure which is directed through the control valve 14 and the line 13 to the control valve 9. This same actuating pressure also communicates through the pressure line 11 and a throttle 12 to the fluid pressure cylinder 24 to move the piston 22 against the force of the spring 26 but only after the accumulator pressure is already communicated to the suction or high pressure line 2 for the fluid motor 3.

The pump motor 32 is advantageously electrically connected to the actuating pressure source 28 through a connection 34 and also through a connecting line 36 to the control valve 14. When the drive motor 32 is started the valve 14 is adjusted electrically to connect the actuating pressure source to the pressure line 11 and the control line 13. When the pump 32 is stopped the control cylinder 24 is connected through the pressure line 11 back through the control valve 14 to the sump 3 and this permits actuation of the brake piston 22 by the biasing means 26.

In the embodiment shown the throttle 12 comprises a delay device for delaying the communication of the actuating pressure to the brake control cylinder 24 but any suitable delay device may be provided for this purpose. The delay device has the effect that the brake comes into action with an adjustable time delay after the delivery volume of the pump 1 drops to zero. When the lifting of a load is ended, the hydraulic pump] is switched off at which time the holding brake mechanism 7 is brought into action with some delay. The load then will remain at the same height and will not suddenly drop due to the unwinding of the winch drum 6. The pressure in the high pressure conduit 2 falls below the load pressure but the releasable non return valve 9 closes so that the operating pressure is stored in the accumulator 10 which corresponds to the load pressure which was previously prevailing.

When the holding brake 7 is released and the hydraulic pump is started again, in a period of time which can be regulated by the throttle element 12 the releaseable non return valve 9 is first opened to communicate the accumulator pressure 10 to the fluid motor 3 so that it will be backed up by a pressure corresponding to the load pressure. Thereafter the brake is released and the hydraulic motor 1 is again brought into action without any undesirable sinking of the load.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. In a fluid motor driven system for driving a rotatable shaft adapted to be connected to a load which is lifted and which has an actuating pressure source, a brake for stopping the shaft which is actuated by an actuating pressure source and in which a pump provides a fluid pressure discharge into a line connected to operate a fluid motor to drive the shaft, the improvement comprising an accumulator connected to the connection between the pump and the motor with means in said connection for permitting the actuating pressure source to be communicated to said accumulator, and an actuating pressure connection from the actuating pressure source to the brake for operating the brake and to the accumulator for operating the accumulator to connect the accumulator to the fluid motor before the brake is released.

2. A fluid drive system for a winch and similar lifting device, comprising a fluid drive motor having a drive shaft adapted to be connected to the lifting device, a brake connected to said drive shaft having a brake applying member which is engageable with said shaft for stopping said shaft, a brake control cylinder, a piston slidable in said control cylinder and engaged with said brake applying member for actuating said member to stop said shaft, means biasing said piston from one side of said cylinder to engage said brake applying member to stop said shaft, said piston being shiftable by brake actuating pressure against said biasing means, a control cylinder pressure line connected to said brake cylinder on the side opposite to said biasing means, an adjustable throttle member in said pressure line, a fluid drive pump having a pump discharge connected to said drive motor to drive said drive motor to rotate said shaft, a pressure accumulator having a pressure release valve connected to said pressure line for actuation by pressure therein, an accumulator pressure line connected from said accumulator to the communication between said pump discharge and said motor to supply accumulator pressure to said motor before the release ofsaid brake, a valve control connected to said pump and to said pressure line venting said control cylinder when said piston actuates said brake but connecting said control cylinder to a source of actuating pressure to release said brake, a source of actuating pressure connected to said valve control, said throttle being set so that said actuating pressure acts on said release valve to connect said accumulating pressure to said motor before said brake is released.

3. A drive according to claim 2, wherein said pressure release valve comprises a releasable non return valve permitting flow from the connection between said pump 'and said fluid motor to said accumulator during operation of said pump.

4. A drive according to claim 2, wherein said valve control is connected to said actuating pressure source and to an electric motor for driving said pump and including an electric motor connected to said pump for driving said pump, said release valve having a branch connection to said section between said valve control and said brake control cylinder.

5. A drive acording to claim 2, wherein said throttle is adjustable. 

1. In a fluid motor driven system for driving a rotatable shaft adapted to be connected to a load which is lifted and which has an actuating pressure source, a brake for stopping the shaft which is actuated by an actuating pressure source and in which a pump provides a fluid pressure discharge into a line connected to operate a fluid motor to drive the shaft, the improvement comprising an accumulator connected to the connection between the pump and the motor with means in said connection for permitting the actuating pressure source to be communicated to said accumulator, and an actuating pressure connection from the actuating pressure source to the brake for operating the brake and to the accumulator for operating the accumulator to connect the accumulator to the fluid motor before the brake is released.
 2. A fluid drive system for a winch and similar lifting device, comprising a fluid drive motor having a drive shaft adapted to be connected to the lifting device, a brake connected to said drive shaft having a brake applying member which is engageable with said shaft for stopping said shaft, a brake control cylinder, a piston slidable in said control cylinder and engaged with said brake applying member for actuating said member to stop said shaft, means biasing said piston from one side of said cylinder to engage said brake applying member to stop said shaft, said piston being shiftable by brake actuating pressure against said biasing means, a control cylinder pressure line connected to said brake cylinder on the side opposite to said biasing means, an adjustable throttle member in said pressure line, a fluid drive pump having a pump discharge connected to said drive motor to drive said drive motor to rotate said shaft, a pressure accumulator having a pressure release valve connected to said pressure line for actuation by pressure therein, an accumulator pressure line connected from said accumulator to the communication between said pump discharge and said motor to supply accumulator pressure to said motor before the release of said brake, a valve control connected to said pump and to said pressure line venting said control cylinder when said piston actuates said brake but connecting said control cylinder to a source of actuating pressure to release said brake, a source of actuating pressure connected to said valve control, said throttle being set so that said actuating pressure acts on said release valve to connect said accumulating pressure to said motor before said brake is released.
 3. A drive according to claim 2, wherein said pressure release valve comprises a releasable non return valve permitting flow from the connection between said pump and said fluid motor to said accumulator during operation of said pump.
 4. A drive according to claim 2, wherein said valve control is connected to said actuating pressure source and to an electric motor for driving said pump and including an electric motor connected to said pump for driving said pump, said release valve having a branch connection to said section between said valve control and said brake control cylinder.
 5. A drive acording to claim 2, wherein said throttle is adjustable. 